Peas (Pisum sativum) are one of the four most important crops next to soybean, groundnut, and beans. It is a particularly important legume in temperate areas with numerous food (dry seed, vegetable) and feed (seed, fodder) usages.

1. P
eas (Pisum sativum) are one of the
four most important crops next to
soybean, groundnut, and beans. It
is a particularly important legume
in temperate areas with numerous food
(dry seed, vegetable) and feed (seed, fodder)
usages.
Field peas have attracted con-
siderable attention as an animal
feed due to increased produc-
tion in Europe and Canada and
thus reliable supply and com-
petitive price. Peaseed meal has
been trialed in Atlantic salmon,
Rainbow trout and European sea
bass with encouraging results.
Peas, when unprocessed, con-
tain moderate levels of protein
22-25 percent but also several
anti-nutritional factors (ANF);
however, the levels of ANFs in
peas are low compared with
other legumes and peas did not
induce enteritis in the distal intes-
tine in Atlantic salmon as seen
when feeding soybean meal.
New feed processing tech-
nologies have provided more
suitable products for use in high
protein aquafeeds. Pea protein
concentrate (PPC) is produced
by fine grinding dehulled peas
into pea flour, followed by air
processing which separates the
particles based on differences in
size and density. The resulting
concentrate has higher protein
and lower carbohydrate and
ANF contents compared with unprocessed
peas, and thus would be a promising protein
source in aquaculture feeds.
The following study examined the efficacy
and nutritional properties of peaseed protein
concentrate as an alternative feed ingredi-
ent and protein source for all-male tilapia
(Oreochromis niloticus) culture incorporating
growth and digestibility trials.
Fish and rearing conditions
Genetically male Nile tilapia (GMT) were
sourced as fry from Fishgen
Ltd and raised at the Centre
for Sustainable Aquaculture
Research at Swansea
University until they reached
the appropriate sizes to be
used in the trials. Fish were
cultured indoors as part of a
freshwater recirculation sys-
tem, which included mechani-
cal and bio-filtration units, a
protein skimmer and a sand
filter. Water temperature
was kept at 27°C and pho-
toperiod was set at 12 hours
of light daily. Temperature
and dissolved oxygen levels
were measured daily, while
total ammonia nitrogen,
nitrite, nitrate and pH were
measured weekly to assure
optimum water quality.
Feed preparation
Feeds were prepared
according to Table 1 by mix-
ing the dry ingredients with a
binder and water, extruded
through a meat grinder and
afterwards dried at 450C for
24 hrs. The resulting pellets
had a diameter of 2.5mm and
3.5mm for growth and digest-
Pea Seed protein
concentrate in
Tilapia feeds
Table 1: Apparent digestibility coefficients (%) of fish meal and pea seed protein as
determined in tilapia
Dry matter
%
Protein
%
Organic Matter
%
Energy
%
Fish meal* 72.1 ± 0.2 89.5 ± 0.2 82.7 ± 0.3 83.7 ± 0.4
Pea seed concentrate** 73.2 ± 0.1 88.4 ± 1.8 79.3 ± 2.2 80.3 ± 2.3
Table 2: Formulation and composition of experimental feeds (per kg as fed)
Ingredients Fishmeal 30% PPC 60% PPC 100% PPC
Formulation
Fish meal 605 410 210 -
Pea seed concentrate - 165 340 520
Corn Starch 325 340 320 310
Vegetable Oil 40 45 50 55
Vitamin &Mineral 5 5 5 5
Di-calcium- Phosphate - - 25 55
Calcium carbonate - - 25 55
Alginate 25 25 25 25
Composition
Dry matter, g 927 905 903 910
Ash, g 133 98.7 92.9 88.8
Lipid, g 86.6 85.6 84.9 83.6
Crude Protein, g 393 390 393 397
Gross Energy, MJ 17.90 18.00 18.08 18.32
Digestible Protein*, g 352 348 349 351
Digestible Energy*, MJ 14.79 14.76 14.67 14.82
DP/DE ratio g/MJ 23.8 23.5 23.8 23.7
* Incorporating results from digestibility trial
by Josh Cantril, Centre for Sustainable
Aquaculture Research, Swansea
University, Swansea, UK and Ingrid
Lupatsch, Aqua Nutrition Manager, AB
Agri Ltd
12 | INTERNATIONAL AQUAFEED | September-October 2015
FEATURE

2. ibility trial respectively and were stable up to
24 hours in water.
Sample preparation and
chemical analyses
At the start of the growth trial samples
of about 10 fish were taken and at the end
10 fish from each tank were sacrificed and
blended to create homogenous samples. Sub-
samples for estimation of dry matter were
taken before the remaining homogenate was
oven-dried. The dried samples were once
more mixed in a blender before all remaining
analyses.
Identical analyses were applied for diets,
faecal matter and body homogenates. Crude
protein was measured using the Kjeldahl tech-
nique and multiplying N by 6.25. Ash was cal-
culated from the weight loss after incineration
of the samples for 12h at 5500C in a muffle
furnace. Gross energy content was measured
by combustion in a Parr bomb calorimeter
using benzoic acid as the standard. Chromic
oxide was estimated by wet digestion.
Feed and faeces containing Cr2O3 were
digested in a mixture of perchloric acid, con-
centrated sulphuric acid and Na-molybdate.
The resulting dichromate was determined at
360 nm against Cr2O7 standard solutions.
Digestibility trial
Digestibility of the pea seed protein con-
centrate was assessed by adding chromic
oxide, an 0.8 percent inclusion, as the indi-
gestible marker to the feed and collecting the
faecal matter by siphoning. By assessing the
ratio of marker to energy or nutrient in the
feed compared to their ratio in faecal matter,
digestibility of the nutrients can be established.
Fishmeal was used as the reference ingredient
and the test diet was mixed at a ratio of 50
percent fishmeal and 50 percent pea seed
protein. Fifteen tilapia, weighing on average
400g, were stocked in 300L tanks to supply
two replicates per treatment. Faecal matter
from a given tank was pooled over the trial
period until sufficient material was collected
for subsequent analyses. Digestibility of ingre-
dients were calculated using well established
equations and are presented in Table 1.
Growth trial
Four experimental diets were formulated
Table 3: Performance parameters of tilapia after 35 days of growth at 27oC (mean ± SD)
Treatment Fishmeal 30% PPC 60% PPC 100% PPC
Initial weight (g) 32.2 ± 1.0 32.5 ± 0.6 32.7 ± 1.2 33.4 ± 0.6
Final weight (g) 97.8 ± 2.2 105.7 ± 1.0 100.9 ± 4.1 65.7 ± 3.2
Weight gain g/fish/day 1.88 ± 0.03 2.09 ± 0.01 1.95 ± 0.08 0.92 ± 0.07
Feed intake g/fish/day 2.06 ± 0.05 2.23 ± 0.12 2.09 ± 0.06 1.07 ± 0.02
FCR 1.10 ± 0.05 1.06 ± 0.06 1.07 ± 0.02 1.16 ± 0.08
Survival (%) 97 ± 4 100 ± 0 97 ± 4 82 ± 8
Table 4: Composition of tilapia per g live weight (mean ± SD)
Initial Fishmeal 30% PPC 60% PPC 100% PPC
Dry Matter, mg 230 248 ± 0.7 274 ± 0.4 266 ± 1.2 247 ± 0.2
Crude Protein, mg 127 139 ± 0.4 150 ± 4.0 149 ± 12.1 133 ± 2.1
Lipid, mg 43.1 65.3 ± 4.0 80.9 ± 1.0 77.0 ± 1.0 63.7 ± 0.4
Ash, mg 59.2 43.6 ± 2.4 43.2 ± 0.8 40.1 ± 1.1 50.4 ± 0.8
Gross Energy, kJ 4.52 5.59 ± 0.18 6.63 ± 0.24 6.37 ± 0.37 5.29 ± 0.0
September-October 2015 | INTERNATIONAL AQUAFEED | 13
FEATURE
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to contain 40 percent protein
and nine percent lipid and
to gradually include pea seed
concentrate at the expense of
fishmeal (Table 2). Seventeen
tilapia of 35g initial size were
stocked in 150L tanks provid-
ing two replicates per treat-
ment. The trial lasted 35 days
and fish were fed manually
to apparent satiation up to 4
times daily. Any uneaten pel-
lets were collected at the end
of the day and accounted for.
Thus feed intake was
quantified and evaluated in
relation to growth response.
Through comparative body composition
of fish carcass the relationship between
dietary protein and energy intake and pro-
tein and energy deposition was assessed,
which allowed estimation of the utilisation
efficiency of the feeds.
Results and Discussion
Comparison of growth performance
among fish showed no difference when
PPC supplied up to 60 percent of the
protein in the diet. But growth obviously
deteriorated in tilapia fed the 100 percent
pea seed diet compared to the other three
feeds. Survival was also slightly reduced
(Table 3).
Despite the poorer growth performance,
results in Table 3 indicate that FCR was not
different among the treatments (Table 3).
Furthermore a trend can be inferred that fish
performance improved with the inclusion
of the pea seed concentrate. This differ-
ence was not proven to be significant, but
nevertheless higher weight gain, improved
FCR (Table 3) and increased energy content
(Table 4) can be described which ultimately
resulted in improved energy and protein
retention efficiencies
(Table 5).
The reduced weight
gain was thought to be
correlated with reduced
feed intake in fish fed the
100 percent pea seed
feed as indicated in Table
3.
Conclusions
Tilapia performed on
feeds with pea seed pro-
tein of up to 35 percent
dietary inclusion very
well. At this level - equiv-
alent to 65 percent of
fishmeal protein replacement - performance
of tilapia was equivalent to fish when fed
the all fishmeal feed.
The reduced growth of tilapia fed the 100
percent pea seed feed was mainly due to
decreased feed intake and palatability might
have been an issue. No significant differences
were found with regards to FCR, energy and
protein retention efficiency values. This fact
supports the notion that whichever pro-
tein source the fish consumed they utilised
equally well.
References available on request
Table 5 : Energy and protein retention efficiency (mean ± SD) in tilapia fed pea seed meal at
increasing inclusion levels.
Fishmeal 30% PPC 60% PPC 100% PPC
Digestible Energy intake
(kJ / fish /day)
30.5 ± 0.8 32.9 ± 1.7 30.7 ± 0.9 15.9 ± 0.2
Energy gained
(kJ / fish /day)
11.5 ± 0.3 15.8 ± 0.6 14.1 ± 1.7 5.6 ± 0.3
Digestible Energy
retention efficiency (%)
37.7 ± 0.0 47.2 ± 0.7 46.0 ± 4.2 35.4 ±1.5
Digestible Protein intake
(g / fish /day)
0.73 ± 0.02 0.77 ± 0.04 0.73 ± 0.02 0.38 ± 0.01
Protein gained
(g / fish /day)
0.27 ± 0.00 0.34 ± 0.01 0.31 ± 0.05 0.13 ±0.01
Digestible Protein
retention efficiency (%)
37.5 ± 1.5 43.4 ± 1.0 42.7 ± 5.4 34.4 ±1.0
14 | INTERNATIONAL AQUAFEED | September-October 2015
FEATURE

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